Synthesis of Aliphatic Amines and Substituted Pyridines Over HZSM",5 Catalyst

Indian Journal of Chemistry Vol. 30A, December 1991, pp.1041-1043

Synthesis of aliphatic amines and tom. The products were analyzed using'5% SE-30 substituted pyridines over HZSM",5 and carbowax columns by gas chromatography. The catalyst' mass spectra were used to confirm the product ana- lysis.

SJKu1karni* & M Subrahmanyam Results and discussion Indian Institute of Chemical Technology, Hyderabad 500 007, The reaction of propylene oxide with ammonia in India water was carried out over HZSM-5 catalyst in the Received 18 June 1991; revised 5 August 1991; accepted range 300-400°C (Tables 1 and 2). Above 220°C, 9 September 1991 the conversion with respect to propylene oxide was The reactions of propylene oxide, propylene glycol, 100 percent and the formation of picolines de- ethylene glycol and acetaldehyde with ammonia have creased with the increase in temperature from 300 been carried out in the temperature range 220°C-450°C to 400°C. The maximum selectivity to 2-picoline with water as diluent. The major products obtained are was 12.0 percent at 300°C with the reactants to wa- methylamine, ethylamine, picolines and acetone. The ter ratio (by volume) was 1:1. The increase of water reaction schemes are proposed based on the product in the feed decreased the picoline formation. The al- distribution. The reactions of acetaldehyde or propylene iphatic amines, particularly, methylamine, ethyla- glycol with ammonia lead to picolines in high yield over mine and acetone were invariably observed in the HZSM-5 catalyst. products in the temperature of 220 to 400°C.

The substituted pyridines like picolines are useful intermediates in the preparation of herbicides, Table I-The effect of temperature on the product distribution in the reaction of propylene oxide with ammonia over HZSM-5 pharmaceuticals and surface-active agents. Pico- catalyst lines are prepared from acetaldehyde and ammonia Temperature/fC 300 350 400 over Pd-Al20~ promoted by PbO, CuO or over [(PrO + NH3)/H20)J by volume 1:1 1:1 1:1 Si0 -Al 0 promoted by Th0 , ZnO or CdO with 2 2 3 2 WHSV/h-1 1.0 1.9 1.9 40-60 per cent yield in the case of 2- and 4-pico- Time onstrearn/hr 1 (1 + 2) 1 lines. The aliphatic amines which are formed in Conversion (percent) 100 100 100 these reactions are also useful in various organic Selectivity to 2-picoline 12.0 11.6 2.0 syntheses 1. In this paper, we report reactions of Selectivity to 3-picoline 8.0 2.4 3.2 propylene oxide, propylene glycol, ethylene glycol Selectivity to pyridine 2.0 2.4 2.0 or acetaldehyde with ammonia over HZSM-5 catalyst. Selectivity to acetone 4.8 4.0 5.6 PrO:NH3 = (1: 1) molar; The other major products were aliphatic amines. Experimental ZSM-5 was synthesized by the method of Argau- er and Landolt-. The Xvray diffraction pattern and Table 2-The effect of temperature on the product distribution IR spectra confirm the typical ZSM-5 structure. in the reaction of propylene oxide and ammonia over HZSM-5 The template was removed by heating the as-syn- catalyst thesized catalyst at 550°C for 15 hr in air. NaZSM-5 Ternperature/f'C 220 250 300 350 400 [(PrO + NH3)/HPl volume 1:2 1:2 1:2 1:2 1:2 was treated with NH4CI solution for long time rep- eatedly. The catalyst was filtered and washed till WHSVlhr-1 1.95 1.95 1.95 1.95 1.95 free from chlo ride ion. The catalyst was activated at Time on streamlhr 1 . 1 (1 +2) 4 1 550°C for 15 hr to obtain HZSM-5. The catalyst Conversion (percent) 100 100 100 100 100 was pelleted, crushed and sieved to 18-30 mesh size. Selectivity to 2-picoline 9.6 6.00 2 The reactions were carried out using tubular Selectivity to 3-picoline trace 4.2 2.4 down-flow pyrex reactor (1.5 em dia).The reaction Selectivity to pyridine trace 5.4 3.6 mixture was fed from top using sage syringe pump. Selectivity to acetone trace 1.2 20.4 12.00 The product was cooled and collected at the bot- The other products were aliphatic amines (methylamine as a major). tIICT Communication No. 2783

1041 INDIAN J CHEM, SEC A, DECEMBER 1991

Table 3 - The reactions of propylene oxide, propylene glycol, ethylene glycol and acetaldehyde with ammonia over HZSM- 5 catalyst Reaction Propylene oxide Propylene glycol Ethylene glycol Acetaldehyde + + + + NH3 NH3 NH3 NH3 Temperature/X' 400 400 400 400 (ReactantslWater) by volume 1:1 1:1 1:2 '1:2 WHSV/hrl 1.9 1.9 1.95 1.95 Time on strearnlhr 1.0 (1+2) (1+2) Conversion (percent) 100 100 90 100 Selectivity (mole percent) 2.0 21.2 1.60 6.16 to 2-picoline Selectivity (mole percent) 3.2 trace trace 3.60 to 3-picoline Selectivity (mole I?ercent) 5.6 37.6 8.8 28.8 to acetone The other major products were aliphatic (C: and Cz) arnines.

The reaction of propylene glycol witn ammonia 3S0-4S0°C. Aliphatic amines were obtained as solution in water was carried out over HZSM-S in major products and picolines as minor products the temperature range of 3S0-4S0°C. The major (Table 3). At 400°C, with the molar ratio, ethylene products obtained were methylamine, ethylamine, glycol: NH3 equal to 1:1, the aromatics were not ob- acetone and substituted pyridines (Table 3). With served in the products. The probable reaction path the increase in propylene glycol in the feed (2:1 is shown in Scheme 2. mole ratio) at 400°C, the aromatic products like CHZOH + NH3 --~- benzene, toluene and xylenes were observed. The I aromatic products might be due to the side reaction CHZOH of propylene glycol over HZSM-S3. The conversion l-HZO was about 100 percent with respect to propylene HZC glycol at 400-4S0°C and first hr on stream. The 1 <,0 + NH3 --~ ••_ H2~::NH + HZO HZC/' probable reaction routes based on product distribu- .HZC ! tion are given in Scheme 1. In the reaction of propy-

CH3CHZNHZ + ~'CH3

Scheme 2: Reaction of ethylene Illycol with ammonia

The reaction of acetaldehyde with aqueous ammonia solution was carried out over HZSM-5 at 400°C. The major products obtained were picolines, aliphatic amines and acetone. With the increase in acetaldehyde (2:1 mole ratio), the conversion to aromatics increased", The overall reaction CH3-CH-CHZ 1 \ / might be depicted as given in Scheme 3 • The selec- N H Scheme 1: Reaction of propylene Illycol with ammonia lene glycol with ethylenediamine over HZSM-S ca- CH3-CH-CH-CHO+CH3CHO+NH3 - (J-CH3+2H20 + H2 N talyst at 400°C, the major products were piperazine ( p-,o-) and 2-methyl pyrazine with 100 percent conver- Scheme 3: Reaction of acetaldehyde with ammonia sion '. The reaction of propylene glycol with ethylenediamine is bimolecular and occurs by intermo- tivity to picolines is more in the reaction of acetalde- lecular dehydrocyclization, Reaction of propylene hyde to ammonia compared to the other reactions glycol with ammonia is a multis~ep, multimolecular studied. This is attributed to the ease with which the process. dehydration of - CHO group takes place over The reaction of ethylene glycol with ammoniacal HZSM-5 catalyst. The cyclization of aliphatic mon- solution in water was carried out over HZSM-5 at oamines formed as products is more difficult

1042 NOTES

Table 4- The reaction of acetaldehyde with aqueous ammonia 3-picoline were major products. Due to water in the over HZSM-5 catalyst feed the aromatics in the product were reduced. Reaction CH)CHO + NH) CH)CHO + HCHO + NH) The reaction of propylene glycol, propylene oxide or ethylene glycol with ammonia is not reported Temperature °C 400 350 400 350 so far. While the reaction of acetaldehyde with am- WHSVlhc1 1 1 1 I monia is reported in patents. Chang and Lang re- Time on streamlhr 111 1 ported 40 to 60 wt % yield of picolines and 78% of Conversion (percent) 100 90 100 100 conversion. They also got lutidines and heavy pro- Selectivity to pyridine 2.53 3.161 6.32 6.96 ducts over ZSM-type catalysts. In case of morden- Selectivity to 2-picoline 4.27 948 2.21 6.64 ite NaX, the catalyst deactivation by coking was Selectivity to 3-picoline 1.90 3.8 rapid", Our results suggest that the yield of picoline Selectivity to 4-picoline 2.06 4.43 is less due to the presence of water. The steam also The other major products were aliphatic amines and acetone reduces the formation of lutidines, heavy products About 10-15 per cent (by volume) aromatics were observed and aromatics.

Acknowledgement through dehydrogenation process over HZSM -5 ca- We are thankful to Dr. A.Y. Rama Rao, Director, talyst. The experimental results are given in Tables 3 IIcr, Hyderabad for the helpful discussions and and 4. support. The results of the reactions of acetaldehyde with aqueous ammonia and acetaldehyde and formalde- References hyde with aqueous ammonia solution at 350°C and 1 Golunski S E & Jackson D, Appl Catal, 23 (1986) 1 and refer- 400°C are given in Table 4. The major products ences therein. were aliphatic amines, pyridines, picolines and ace- 2 Argauer RJ & Landolt G R, US patent, 3702886 (1972). tone. Aromatic products (10-15% by volume) were 3 Kulkarni S J, Subrahmanyam M & Rama Rao A V, Appl Catal, also observed. The striking observation was without Communicated (1990). formaldehyde in the feed, 2- and 4-picolines were 4 Kulkarni S J, Subrahmanyam M & Rama Rao A V (unpu- blished results). the major products. On the other hand, with for- 5 Chang CD & Lang W H, US patent, 4220783 (1980). maldehyde also in the feed (Table 4) pyridine and 6 Venuto PB & Landis P S,.Advances in Catal; 18 (1968) 344.

1043